This invention relates to liner and shell of thermally insulated walls that are used in the lined exhaust systems used to carry or direct hot air or exhaust gases.
Typically, hot gases are produced as a result of a reaction or thermodynamic process such as those that are produced from combustion engines. One result of a combustion process is hot gases which range from temperatures between 750xc2x0 F. and 2000xc2x0 F. As these gases exit the thermodynamic process, they are exhausted into the atmosphere, a duct system and/or chimney or stack depending on the application. These are considered to be types of exhaust systems. Because these systems operate from several hours a day up to 24 hours per day for 20 or more years, it is imperative that the exhaust system components have the durability to withstand the extended and severe operating conditions to which they are subjected.
Generally, in industrial and commercial applications, a duct system and/or chimney or stack, depending on the application is accessible to workers. For safety purposes, surface temperature of equipment that is accessible to workers should be limited 140xc2x0 F. as per ASTM C1055-99, which is recognized as the national consensus standard. This means that if the gases inside the exhaust system are greater than the allowable exterior duct temperature, the duct needs to be either cooled, shielded or insulated.
One method of insulating exhaust systems is through the use of a liner. A liner is a barrier that protects insulation applied inside a duct shell. Typically the liner is coupled to the shell while retaining the insulation necessary to reduce the heat transmitted to the exhaust system shell exterior. The liner is directly exposed to the heat from the hot gases being directed by the exhaust system. Since the liner is exposed to extremely high temperatures, thermal expansion often creates unusual problems such as warping and buckling.
Typical stresses in an exhaust system include broadband exhaust noise, low-frequency noise, thermal expansion and contraction, changes in operating conditions, rupture and creep stresses, earthquakes and other various environmental, acoustical and mechanical stresses and strains.
In order to support or mount a liner or liner panel in the exhaust system, the primary method is active mounting. Active mounting uses direct coupling by through metal contact between the liner and the inside of the shell. However, liners with active mounting may not respond well over time to changing stresses and strains as a result of direct exposure to heat.
In order to provide for coupling between the shell and the liner, a passive mounting system is provided. The passive mounting system uses indirect metal contact between the liner or liner panel and the shell. The through-metal contact, or direct contact, is insignificant for this method of mounting.
This design serves two main objectives: to minimize heat transfer between the hot gases and ultimately the exterior of the exhaust system; and to provide flexibility and mobility between liner components for changing stress and strain conditions, whether thermally related or otherwise.
A passive mounted lining system comprising an outer shell, a liner support channel having a bolt slide void, a partially threaded bolt with a predetermined length of threads, a lock washer with a void disposed thereon, a first washer with a void disposed thereon, a spacer with a void disposed thereon, a first graphite layer with a void disposed thereon, a liner panel having a liner panel void, a second graphite layer with a void disposed thereon, a second washer with a void disposed thereon, a nut with a void disposed thereon, wherein the liner support channel is carried by the outer shell, and wherein the partially threaded bolt is slidably engagable with the bolt slide void, and the bolt carries the lock washer, the first washer, the spacer, the first graphite layer, the liner panel, the second graphite layer, the second washer, and wherein the nut is threadedly engageable with the bolt.
One objective of the present invention is for the disclosed method and apparatus to capably withstand seismic loads, such as those possible in seismic zones 3 and 4 as described by ANSI and ASCE design standards.
A method of mounting a liner system is also disclosed, the method comprising providing an outer shell, mounting on the outer shell a liner support channel having a bolt slide void, providing a partially threaded bolt with a predetermined length of threads in sliding engagement with the bolt slide void, mounting successively on the bolt a lock washer, a washer, a spacer, a graphite layer, providing a liner panel having a liner panel void, mounting the liner panel on the bolt through the liner panel void, mounting on the bolt a graphite layer, a washer, and a nut. The method further comprises tightening the nut on the partially threaded bolt, while not binding the liner panel. The method further comprises peening exposed threads that extend vertically past the nut to prevent the nut from loosening, or welding one face of the nut to the second washer to accomplish the same objective. It should be noted that the nut, the washer, the liner panel, the graphite layer, the graphite layer, the spacer, the washer and the lock washer are all provided with voids larger in diameter than the bolt.